It is known to bond a nonwoven mat or fleece of thermoplastic synthetic resin filaments (e.g. spun bond) or fibers (e.g. melt blown) to a foil of synthetic resin material and even to apply the synthetic resin material as a melt to the mat or fleece from a wide-slit nozzle so that, upon congealing, the melt will form a foil.
It is also known, in the fabrication of synthetic resin webs to utilize biaxially stretched mats or webs, i.e. webs or mats which have been stretched both in the longitudinal and transverse direction to improve the mechanical properties of the mat or fleece.
In German Patent Document DE 195 34 702 A1), moreover, it is taught to use an electrostatic charge to create force fields which press the foil onto the nonwoven fleece web or mat.
While biaxial stretching has been carried out in the past, the nonwoven mat has been subject to such stretching before the mat reaches the bonding roller on which the foil is applied to the mat so that the plastic foil will remain unstretched.
Composite webs fabricated with such nonwoven mats or fleeces heretofore have generally been found to be satisfactory for many purposes. However it has been found that composite materials are desirable where the synthetic resin foil component must be especially thin to achieve a desired degree of gas permeability, for example when the web should be capable of "breathing." It has been found to be difficult to handle the extremely thin foils that are necessary for a high degree of gas permeability and to effectively bond such foils to the nonwoven mat or fleece because of the low heat capacity of the foils. When the mechanical properties of stretched foils were to be exploited, it was necessary to provide relatively thick foils and that interfered with the breathability of the composite.